Program to Accept value of Radius and Calculate Area of Circle.

class CalculateCircleAreaExample
{

    public static void main(String[] args)
    {

        int radius = 3;
        System.out.println("The radius of the circle is " + radius);

 /*
         * Area of a circle is pi * r * r where r is a radius of a circle.
  */

        // NOTE : use Math.PI constant to get value of pi
        double area = Math.PI * radius * radius;

        System.out.println("Area of a circle is " + area);
    }
}